The present invention relates to a carburetor control system for a motor vehicle including an apparatus to maintain the vehicle in running at some desired speed and more particularly to an arrangement to prevent the slack of a core of a pulling type accelerator wire which transmits motion of an accelerator to the vehicle carburetor.
FIGS. 1, 2A and 2B illustrate a carburetor control system including an apparatus to maintain the vehicle in running at some desired speed, which apparatus aims at lessening the fatigue of a driver by releasing him or her from stepping on an accelerator to maintain the vehicle speed.
Referring to FIG. 1, an accelerator pedal 1 is in an operative engagement with one end of a pedal lever 3 whose opposite end is connected to one end of a core 4a of an accelerator wire 4, the lever 3 being rockably mounted to a bracket 2, fixed to a vehicle body (not shown), at its intermediate portion. Referring also to FIGS. 2A and 2B, the opposite end of the core 4a is provided with an anchor 4c with which the opposite end thereof is anchored to a fan-shaped member 7 at a portion adjacent the remote one of side edges thereof. The member 7 is connected at a root portion thereof to a torsion shaft 6 for rotation therewith, the torsion shaft 6 being connected to a throttle blade of a carburetor, not shown, for controlling an angular throttle position of the throttle blade. As best seen in FIG. 2B, the core 4a passes along the circular periphery of the fan-shaped member 7. With a return spring 8, the fan-shaped member 7 is biased in a direction indicated by an arrow b, the return spring 8 having one end engaging the fan-shaped member 7 and an opposite end engaging a fixed portion of a vehicle body 25. An idler lever 9 is rockably mounted to the torsion shaft 6 and biased in a direction indicated by an arrow c by means of a tension spring 10 having one end engaging an end of the idler lever 9 and an opposite end engaging the adjacent fixed portion of the vehicle body 25. The idler lever 9 is formed with an engaging ear portion 11 projecting laterally from an intermediate portion thereof for abutting engagement with the remote one of the side edges of the fan-shaped member 7 so that rocking the idler lever 9 in the opposite direction to the one directed by the arrow c will urge the fan-shaped member 7 to rock in the opposite direction to the one directed by the arrow b. Since the spring 8 biases the fan-shaped member 7 into engagement with the ear 11, the fan-shaped member 7 will swing together with the idler lever 9 as the latter is swung by a core 12a of a wire 12 leading to an apparatus to maintain the vehicle in running at a desired speed. One end of the core 12a engages the idler lever 9 at the opposite end thereof to the end engaged by the spring 10, while, the opposite end of the core 12a engages one end of a rod 13b whose opposite end is securely fixed to a diaphragm 13a of a diaphragm device 13. Designated by the reference numeral 16 is a so-called three-way solenoid valve, i.e., a solenoid actuated selector valve which selectively establishes an air flow communication between a vacuum pipe 14 leading to a source of vacuum, such as, the engine intake manifold, and a pipe 24 leading to a power chamber 13c of the diaphragm device or an air flow communication between a bleed pipe 15 leading to the ambient atmosphere and the pipe 24. The solenoid valve 16 has a solenoid, not shown, selectively energized under the control of a controller 17. Designated by the reference numerals 18 and 19 are a vehicle speed sensor and a switch operable by a driver. When the driver turns on the switch 19, the controller memorizes a vehicle speed at this instance so as to supply a control signal to the solenoid of the solenoid valve 16 by comparing the vehicle speed memorized with an actual vehicle speed subsequently detected by the vehicle speed sensor 18. In response to this control signal from the controller 17, the solenoid selector 16 controls the lever of vacuum within the power chamber 13c by selectively establishing an air flow communication between the pipes 14 and 24 and an air flow communication between the pipes 15 and 24. Since a diaphragm return spring 13d biases the diaphragm 13a and thus the rod 13b to the left so as to permit the spring 10 to biases the idler lever 9 into the illustrated position when the vacuum within the power chamber 13c is lower than a predetermined level, increasing the vacuum within the power chamber 13c above the predetermined level will cause the diaphragm 13a and thus the rod 13b to the left against the bias action of the spring 13d, pulling the wire 12 to rotate the idler lever 9 and thus the fan-shaped member 7, clockwise, to increase an opening degree of the throttle blade. Thus, the angular position of the throttle blade is appropriately controlled to maintain the vehicle speed at the vehicle speed value memorized by the controller 17 at the instance the switch 19 was turned on without manipulating the accelerator pedal 1. When the turned-on state ceases upon turning off of the switch 19, the above mentioned action is cancelled and the solenoid valve 16 returns to an initial or rest condition in which the bleed pipe 15 and the pipe 24 are connected, thus permitting the diaphragm return spring 13d to move the rod 13b to the illustrated position, returning the idler lever 9 to the illustrated position. The cancellation will be effected also by a brake actuation detector switch 20 when the vehicle brake is stepped on, or by an accelerator actuation detector switch 21 when the vehicle clutch is actuated.
Under a condition in which the apparatus is in operation to maintain the vehicle speed at a desired level, when the vehicle begins to climb a steep slope after running on a flat roadway or when, under a cruising condition at some vehicle speed level, the apparatus is rendered operative right after the driver steps off the accelerator 1, the idler lever 9 will be rotated counterclockwise suddenly toward a position corresponding to the fully open position of the throttle blade, thus rotating the fan-shaped member 7 accordingly.
During this motion of the fan-shaped member 7 which will push the core 4a toward a switch stop 4d at one end of an outer casing 4b of the accelerator wire 4, the accelerator, under its weight, will move toward a fully depressed position thereof, pulling the core 4a of the wire 4. However, when this motion of the fan-shaped member 7 is fast, the movement of the accelerator can not pull the core as fast as the core is pushed by the fan-shaped member 7, thus causing the core 4a to slack between the fan-shaped member 7 and the switch stop 4d, as illustrated in dash-dot-line in FIG. 1. This slack causes the core 4a to disengage from the fan-shaped member 7 or causes the core to be bent, shortening its life.
In order to prevent the occurrence of the slack as mentioned above, the weight of the accelerator 1 may be increased. But this necessitates a corresponding increase in biasing force of the throttle return spring 8, resulting in deterioration of the accelerator manipulation feeling. The occurrence of the slack may be prevented by employing, as an accelerator wire, a push and pull type cable. But this cable is so rigid against the bending stress that it reduces the transmission efficiency of the motion between the accelerator 1 and the fan-shaped member 7 and not suitable for the accelerator wire.